Transcript Charente basin polluted by Agriculture

Charente basin
polluted by
Agriculture
16/02/2005
Coste Sabrina
Thessaloniki
Localization and presentation of
the Charente basin
• Superficy 10 549 km2
• Population 585 400
inhabitants
• Density 55,5 inhab/km² (40
à 100 inhab/km²)
• In summer there are 117
445 inhabitants more
• divided in 4 under basin:
–
–
–
–
Charente upstream
Charente downstream
Boutonne
Tardoire Touvre
The 4 under basin
Agriculture :The fact
– An excessive amount of fertilizer (nitrate
and phosphate)
• To improve production of cereals !
– A lack of wetland and bank vegetation
around the river ,so phosphate with organic
materials can leach directly into the river
What is happening ?
• A part of nitrate is taken up by plants
• Phosphate are attached to the soil, and this
mineral must change before it can be
incorporated by plants
– But more of this is staying in the river and
causes damage in water
Eutrophication
• Main influences :
– Big amount of phosphate in the water
– Photosynthesis
– Staining water ( etiage when there is a
prolonged hot summer and excessive
removal of groundwater )
What are the main consequences?
1. Increasing of macrophytes, because
zooplankton can not regulate this big
development.
2. Decreasing of oxygen caused by :
• Development of unicellular algae
• Increasing of bacteria activities which requires a lot of oxygen
to decompose organic material
• Anaerobic bacteria deplete oxygen levels so plants and animals
disappear. Like it happened in the Charente basin (cyprinidae
and rainbow trout)
3. And the phenomenal of cyanobacteria which
uses the atmosphere nitrogen and phosphate
and develops very quickly
Be careful it’s dangerous for human and
phytoplankton because they produce toxic
secretion (DDASS)
Hypothesis for restoration
• Moderate consumption of the groundwater by
the population
• Cultivated land between green bands and
streams
REFERENCE
• http://www.enseeiht.fr/hmf/travaux/CD0102/travaux/optsee/bei/1/g
14/pa04.htm